1. Technical Field
The present technology relates to a pneumatic tire that is ideal for racing, and more particularly relates to a pneumatic tire capable of improving uneven wear resistance and warming up performance, while improving running performance when traveling straight and when cornering on wet road surfaces.
2. Related Art
Tires provided with a plurality of main grooves extending in a tire circumferential direction in a tread portion are normally used as wet tires for racing. It is recognized that superior running performance of such tires on wet road surfaces are exhibited based on a drainage capability of the main grooves. However, in high-speed races, an amount of water pushed back forward increases since water cannot be drained by the main grooves in tires having a tread pattern with main grooves extending in the tire circumferential direction as a main constituent, which results in an occurrence of a hydroplaning phenomenon. Also, in races with GT touring cars having tire housings, there is an adverse effect whereby water remains in tire housings when tires having a tread pattern with main grooves extending in the tire circumferential direction as the main constituent are used. Thus, a groove arrangement that can drain water on road surfaces in a tire lateral direction is required.
As a wet tire for racing meeting such a demand, a tire has been proposed including, in a tread portion, a main groove extending in a tire circumferential direction in a tread center position, a plurality of first angled grooves that is in communication with the main groove and that extends at an angle in a direction opposite a rotating direction from the tread center position toward each shoulder side, and a plurality of second angled grooves that is not in communication with the main groove and that extends at an angle in the same direction as the respective first angled grooves while intersecting at least three of the first angled grooves, wherein a plurality of blocks is partitioned by the main groove and the angled grooves (for example, see Japanese Unexamined Patent Application Publication No. 2007-238060A).
However, when the tread portion is partitioned into a plurality of blocks by the main groove and the angled grooves as disclosed above, a rigidity of the tread portion deteriorates. Since a large load is applied to tires when braking and driving and when cornering in racing, there is a problem that a necessary braking and driving performance and turning performance on wet road surfaces cannot be exhibited when the rigidity of the tread portion is insufficient.
In addition, in recent years, there is a demand to improve uneven wear resistance in addition to running performance when traveling straight and when cornering on wet road surfaces as described above, in order to solve the problem that the required tire performance cannot be obtained due to the occurrence of uneven wear in the tire. Also, in order for a tire to exhibit its intended performance, it is necessary that the tire temperature be a certain temperature, however, in particular on wet road surfaces, it tends to take time until the tire temperature for exhibiting the intended tire performance is reached, so there is a demand to shorten this arrival time (to improve the warming up performance).